✨ PoC: Implement user scopes

[sttts]

Summary

This is towards warrant support in #3156.

Related issue(s)

Release Notes

Add user info support for scopes through the extra key `authentication.kcp.io/scopes: cluster:<name>` to contain a user in a certain cluster.

[kcp-ci-bot]

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[kcp-ci-bot]

@sttts: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-kcp-build-image	8479e5d	link	true	/test pull-kcp-build-image
pull-kcp-lint	8479e5d	link	true	/test pull-kcp-lint
pull-kcp-verify	8479e5d	link	true	/test pull-kcp-verify
pull-kcp-verify-codegen	8479e5d	link	true	/test pull-kcp-verify-codegen
pull-kcp-test-e2e-sharded	8479e5d	link	true	/test pull-kcp-test-e2e-sharded
pull-kcp-test-e2e-shared	8479e5d	link	true	/test pull-kcp-test-e2e-shared
pull-kcp-test-unit	8479e5d	link	true	/test pull-kcp-test-unit
pull-kcp-test-e2e	8479e5d	link	true	/test pull-kcp-test-e2e
pull-kcp-test-e2e-multiple-runs	8479e5d	link	true	/test pull-kcp-test-e2e-multiple-runs

Full PR test history

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